CAD & CAM

Question 1

What is a Datum?

Answer 1

A datum is commonly referred to a start point or reference point

Question 2

What are the Advantages and Disadvantages of Datums?

Answer 2

Advantages
- Create datums on irregular surfaces
- Makes inspections easy by creating datums
- Lower chance of part rejection
- A better quality part is possible
- Fixture design becomes possible

Disadvantages
- Increases inspection cost
- Specialist equipment is required for inspection
- A skilled technician is required

Question 3

What is a Tool Pathway?

Answer 3

The outlined path a machine follows to complete its process

Question 4

What are Dimensional Tolerances? And what are their function?

Answer 4

They show the manufacturer the maximum variation from the original sizes possible
They allow us to ensure parts are sized correctly so they function well

Question 5

What are the 3 different types of Tolerances and what do they look like?

Answer 5

Common Tolerance - shows the original size with the tolerances applied
Symmetrical Tolerance - shows the original size along with the same maximum and minimum tolerance
Asymmetrical Tolerance - shows the size along with the different maximum and minimum tolerances

Question 6

What is the basic symbol for Surface Finish?

Answer 6

A ‘V’ shape with an extended right leg

Question 7

What does it mean if there is horizontal line in the centre of a Surface Finish symbol?

Answer 7

Material needs to be removed

Question 8

What does it mean if there is a circle in the centre of a Surface Finish symbol?

Answer 8

The removal of material is not permitted

Question 9

What does the Centre Of Gravity symbol look like?

Answer 9

A circle with 2/4 black and 2/4 white

Question 10

What is the function of the Centre of Gravity symbol?

Answer 10

It shows the point where an item can balance without toppling

Question 11

What is the purpose of CAD/CAM 3D Printing?

Answer 11

The product can be real life tested
The client can have a visual aid
Allows the manufacturing process to be tested
More cost effective and less destructive

Question 12

What is the process for 3D Printing?

Answer 12

1.Convert the model into an STL file
2.Ensure the volume of the model is suitable for the volume of the 3D printer.
3.Set the requirements for the surface finish
4.Ensure the model is balanced correctly as required by its centre of mass and supports added where required

Question 13

What are the file types commonly used in CAD/CAM?

Answer 13

.DXF and .STL

Question 14

What are Advantages to .STL?

Answer 14

Small file sizes making them easy to transfer and share.
Universally understood by all 3D printing technology.
Acts as an interface between 3D modelling and printing to ensure 3D printers can interpret modelling data for printing.

Question 15

What are Disadvantages to .STL

Answer 15

Only understands the external surface and shape of the 3D model
Can contain gaps and overlaps of joining
surfaces in a model that are not drawn correctly.
These are known as non-manifold edges
Information such as colour, internal structure, texture or attributes that a CAD file holds may not be included in an STL file.

Question 16

What are some Advantages to CAD/CAM

Answer 16

More accurate than traditional production methods
Repetitive nature of robotics results in high efficiency outputs
Faster to produce and less labour intensive due to speed and efficiency of computer systems and CNC machines.
Files can be copied, stored, printed, manufactured and shared electronically as required.
Designs/models can be easily edited and modifications do not generate endless redesign of the original drawings/model.
Processes such as 3D printing result in less destructive testing and utilise materials that can be recycled.

Question 17

What are Disadvantages to CAD/CAM

Answer 17

Initial set up costs can be extremely high.
Traditional skills will be lost as they become unnecessary due to the increased use of robotics and systems
Specialist software, hardware and training is required which costs time
and money.
Difficult to keep up with constantly changing and improving technology

Question 18

Describe Top Down Modelling

Answer 18

Contains one part which is used to model all other components
It ensures all parts fit together
When a change is made to one part, all other parts are changed

Question 19

Describe Bottom Up Modelling

Answer 19

When parts are made individually then assembled to create a final model
If a part is edited, then only that part is updated
This can result in multiple parts being edited to ensure the model is successful

Question 20

What is Polygon Modelling

Answer 20

an approach for modelling objects by representing or approximating their surfaces
using polygon meshes.